This invention relates to probes for use on position determining apparatus such as coordinate measuring machines, measuring robots and in particular machine tools.
An example of such a probe is shown in U.S. Pat. No. 4,153,998. Probes intended for use on machine tools, in which there is a wireless signal transmission system between the probe and the controller of the machine tool, are shown in European Patent Numbers 337669 and 337670.
As such probes have become more complex over the years, there has been a need for them to operate in different modes.
For example, it can be desirable for the signal produced by the probe to be filtered prior to transmitting it to the controller, in order to prevent the generation of spurious signals as a result of vibration. Therefore, the probe may be preset to use different types of filtering, or no filtering, depending on the machine tool and the environment into which it has been installed.
Furthermore, on machine tools such probes are commonly battery operated. The wireless signal transmission system also includes a receiver for receiving a switch-on or start signal. This switches the probe on from a sleeping state in which it consumes very low current, ready for normal use. It is then desirable to switch the probe circuitry off (back to the sleeping state) after use. The probe may have different preset modes, giving different manners in which the circuitry is turned off.
In known probes, such modes are preset by the use of DIP switches on a circuit board internally within the probe. This has a number of disadvantages. In order to change the preset mode, the operator has to dismantle the probe to access the DIP switches. There is a risk that the operator will damage the printed circuit board, and the probe has to be designed to permit such dismantling. Where the DIP switches act on a micro controller to preset the mode, there is a restriction on the number of input lines to the micro controller.
With, say, three such input lines from a three-gang DIP switch, a maximum of eight modes can be preset. Any more modes would require a larger number of input lines to the micro controller. Finally, it would be desirable to provide a pre-setting device which is smaller, less expensive and more reliable than DIP switches.